IO

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Introduction

• Behavior 行为

Input (read once), output (write only, cannot read) ,or storage (can be reread and usually rewritten)

• Partner 交互对象

Either a human or a machine is at the other end of the I/O device, either feeding data on input or reading data on output. 一端一定是CPU <= 数据必须传到CPU处理

• Data rate

The peak rate at which data can be transferred between the I/O device and the main memory or processor.

Performance

Amdahl’s (阿姆达尔)law

Disk Storage and Dependability

Performance

RAID

- 只有最后一个可以在两个错误发生的情况下survive

• Capacity penalty to store redundant info
• Bandwidth penalty to update redundant info

Buses and Other Connections between Processors Memory, and I/O Devices

计算

同步异步的BandWidth

• 地址给Memory
• 读取数据
• 传输数据